Snap action thermostatic switch



y 1937. J. E. CARLSON 2,081,269

vSNAI ACTION THERMOSTATIC SWITCH Filed June 16, 1934 INVENTOR JOHN E.CARLSON,

Patented May 25, 1937 UNITED STATES PATENT OFFICE SNAP ACTIONTHERMOSTATIC swrrcn necticut Application June '16, 1934, Serial No.730,936

5 Claims.

My invention relates particularly to switches which are adapted to beautomatically actuated by changes in'temperature and which areadjustable to vary the temperature range of action.

A special use for this device is in the control of the temperature ofbrooders and the like.

A special object is to provide a simple but reliable form of switchwhich can be made and assembled according to standard specifications andwhich is extremely sensitive and yet reliable.

Another object is to provide a device of this character which can beadjusted with respect to its temperature range and the parts of whichwill be certain to stay in their adjusted position.

In the form shown the invention contemplates a bendable spring arm whichis anchored at one end and connected at the other end with a switchactuating lever mounted on a substantial knife edge which is provided ina bracket which also serves as a stop to limit the movement of thecontact actuating lever. The spring arm is actuated by an expansibledisc or bellows containing a temperature sensitive medium such-as ether.'The actuation of the arm is adjustable by means of a screw threadedmember which is connected to the arm in such a manner as to provide ineffect a spring tension nut lock so that the screw threaded member maybe easily adjusted but will be certain to stay in its proper adjustedposition.

Fig. l is a cross section and side elevation of one form of deviceembodying my invention.

Fig. 2 is a plan view of the switch contact members.

Fig. 3 is an edge view of the same.

Fig. 4 is an end view of the switch contact members.

Fig. 5 is an exploded perspective view of the tip of the spring arm, thecontact actuating lever and the bracket support for the latter.

Fig. 6 is adetail cross sectional view showing the adjusting and clampmechanism.-

A plate l supports the various parts involving my invention and isadapted to be supported, for instance, in the housing of a brooder on awall 8 and a cover 9, the latter being provided with an opening I andlid H which provide access to the device. j

The temperature sensitive element I2 is in the form of a multiple platedisc of suitable type forming a reservoir for the expansible fluid.

' This is supported by a yoke l3 which in turn is It suspended from theplate I. It to supported by a tube The main spring arm I is anchored atbase plate l- An adjusting screw H has a threaded seat It in the arm l5and has a cup-like member l8 at its lower end which engages the upperend of the rod l9 whose lower end rests on the upper face of theexpansible disc l2.

An additional supportfor thescrew I1 is provided by a supplementalspring arm which is secured to the arm l5 and provided with a threadedseat 2| for the screw. When the parts are assembled the arm 20 ispressed down toward the threaded seat I6 when the screw is inserted.When pressure on the arm 20 is released the spring tension takes up allthe play which may exist between the threaded seat It and 2! and thescrew l1 and prevents the screw from accidental turning.

The switch action is directly or indirectly effected by the movement ofthe lever 23 which has knife edge seated in grooves 25 in the bracket26. This bracket is supported by an insulating block 2'! which in turnis mounted on v the upper end of the base plate l.

A spring 28 connects the lever 23 with the tip of the spring arm l5. Aninsulating piece 29 may be provided to serve as the anchor for one endof the spring 28 to insulate the'spring 28 from the arm l5. Bracket 26is provided with a stop shoulder 30 for limiting the movement of thelever 23.

In the form shown the switch lever 23 makes contact in one position witha spring supported contact 35.

The actuation of the switch is effected by the expansion and contractionof the disc l2 which by means of the rod l9 raises the spring arm It toopen the circuit and the spring arm l5 returns the parts to close thecircuit when the disc l2 contracts.

It will thus be seen that the parts are simple in construction andunlikely to get out of order even with rough uses.

By adjusting the screw ll the'tension on the spring arm l5 and on thedisc t2 may be varied so as to alter the action of the switch to controlthe opening and closing of the circuit at th desired temperatures.

I claim:

1. A thermostaticswitch having a pressure device, an arm for actuating aswitch, an auxiliary spring arm having one end secured to the first arm,an adjusting screw having threaded engagement in both arms and a pushrod interposed between said screw and said pressure device.

2. A thermostatic switch device including a base plate, athermalexpansion device suspended from the base plate, a spring arm having oneend secured to the said base plate and having a bowed portionimmediately above the thermal expansion device, an insulating blockcarried by the base plate, a stationary switch contact carried by saidblock, a supporting member carried by said block and having an abutmentshoulder, a switch member hinged to said support and coacting with saidcontact and said abutment, a spring connecting the movable end of thespring arm and the switch member, and an adjusting screw passing throughthe bowed portion of said spring arm and coasting with the thermalexpension device to vary the action of the spring arm and the connectedswitch member.

A thermostatic switch including an arm movable in response totemperature change and having an end portion thereof unsupported, afixed wall substantially normal to said arm, a tension spring passingthrough said wall and connected to the unsupported end portion of saidarm, a plate held against said wall by said spring for pivotal movement,abutments secured with respect to said wall on each side of said platefor limiting movement of the plate, a support forsaid wall andabutments, the abutment remote from said support being connected to saidwall in a manner to extend over and shield and protect the plate and itspivotal engagement.

4. A thermostatic switch including an arm movable in response totemperature change and having an end portion thereof unsupported, afixed wall substantially normal to said arm, a tension spring passingthrough said wall and connected to the unsupported end portion of saidarm, a plate held against said wall by said spring for pivotal movement,abutments secured with respect to said wall on each side of saidplate'ior limiting movement of the plate, a support for said wall andabutments, the abutment remote from said support cooperating with saidplate by means of a projection and recess remote from the plate pivotand shaped to prevent any lateral shifting of said plate along itspivotal axis.

5. A temperature responsive switch having an arm for actuating a switch,a short spring arm having one end secured to .the first arm, anadjusting screw having threaded engagement with both arms and atemperature responsive mechanism connected to said adjusting screw formoving the arms and actuating a switch.

JOHN E. CARLSON.

